“I don’t know what the thinking was behind her walking away,” said a source. “She was offered a very generous deal.”

Abdul’s decision to bolt “Idol” came, pointedly, a day after Fox announced that Kara DioGuardi, who joined the show last season as the fourth judge, would return for another go-round.

It also follows on the heels of show host Ryan Seacrest inking a three-year, $45 million deal to remain with “Idol.” The deal was reportedly for $10 million a year — with the other $5 million earmarked for side projects.

Abdul was reportedly seeking $20 million a year to return to “Idol.”

Simon Cowell and Randy Jackson are both signed through next season, Cowell at a reported $35 million annually.

But Fox was “actively working” to hammer out a new deal with “Idol” lightning rod Abdul, sources say.

And the “Idol” producing triumverate — Fox, FremantleMedia and 19 Entertainment — apparently didn’t appreciate “rude” statements made last month by Abdul’s new manager, David Sonenberg.

In comments to the LA Times, Sonenberg characterized Abdul as “hurt,” “angry” and “not a happy camper” over the prolonged contract talks.

“Her camp tends to be really dramatic about a lot of things,” said the source. “She’d been with [Sonenberg] all of about two weeks when he made those statements.

“A lot of people didn’t even know Paula had signed with a new manager. The negotiations took a different tone thereafter.”

Sonenberg did not return calls yesterday.

The plan, as it stands now, is for “Idol” to soldier on with DioGuardi, Jackson and Cowell.

All three judges will be in Denver tomorrow for the opening round of the “Idol” judges’ auditions.

“I can’t believe it,” Jackson told “Extra.” “It looks to be true.”

Former “Idol” executive producer Nigel Lythgoe called Abdul “a main ingredient” of “Idol” — and said she would be welcome on his Fox show, “So You Think You Can Dance.”